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Qtractor 0.4.6 - The Funky Deviless is here!

So much to tell, even more to do... then one could hardly shake, this long overdue. Lousy rhymes and no miserly times. And there it is: a bug-fix release, I'll mean to ease.

Oh crap! Let's get it through once and for all.

With huge compliments to all who got the nerve and report as many too much idiosyncrasies (nee bugs). Don't, never look back. There's plenty more ahead, no matter where you look, or hear, whether is up or down hill :)

Qtractor 0.4.6 (funky deviless) is here!

Release highlights:

  • MIDI Editor draw mode (aka paint mode) (NEW)
  • MIDI Swing-quantize (NEW)
  • LV2 UI Instance & Data-access extension support (NEW)
  • JACK Session support (EXPERIMENTAL) (NEW)
  • LV2 Save/Restore extension support (NEW)
  • MIDI Editor event list in-line editing (NEW)
  • MIDI Clip time-stretching (FIX)
  • MIDI Clip editor file salvage quietness (NEW)
  • MIDI Control bus switching crash (FIX)
  • MIDI Bank-selection backout (FIX)
  • Initial widget geometry extents (FIX)
  • Input-only bus playback crash (FIX)
  • Bus connection persistence crash (FIX)
  • Drag-and-drop cloning plugins (FIX)
  • MIDI Editor floating-selection persistence (NEW)
  • Audio inserts garbage signal (FIX)

A bit more or not so detailed change-log is found below.


Project page:


Weblog (upstream support; you're already reading it):

License (no kiddin'):

Qtractor is free, open-source software, distributed under the terms of the GNU General Public License (GPL) version 2 or later.


  • Introducing a non-painting edit sub-mode on the MIDI clip editor's piano-roll (see Edit/Select Mode/Edit Draw menu).
  • The MIDI clip editor (aka piano-roll) is now a lot more quiet about saving its own dirty content, delegating all
    salvage questions to main session control.
  • Don't show session restart message box when changing JACK transport mode option anymore.
  • Dedicated MIDI control bus switching fixed. Was closing the wrong bus eventually and crashing the whole show with it (fixes bug #2989590).
  • MIDI bank/program backout has been corrected on MIDI track properties dialog rejection (ie. user cancellation).
  • MIDI bank select method has been corrected for tracks with no instrument defined (probably fixing bug #2987071).
  • LV2 UI Instance and Data Access extension support added; reduce LV2 external UI parameter value update flickering.
  • JACK session infrastructure support. (EXPERIMENTAL)
  • Initial widget geometry and visibility persistence logic has been slightly revised as much to avoid crash failures
    due to wrong main widget hidden state.
  • Initial mixer widget extents are now set reasonably larger.
  • General source tree layout and build configuration change.
  • Ever since smooth-ramping introduction that having at least one input-only buses were causing immediate playback crashes, now hopefully fixed.
  • Refactored for common engine client nomenclature, primarily provided by JACK, then secondarily passed to ALSA Sequencer, getting rid of the JackUseExactName requirement and lifting the unique/single instance restriction in the process.
  • Current JACK Transport, MMC Device, and MIDI Song Position pointer (SPP) control modes are now saved/loaded as part of session option properties.
  • MIDI clip editor's context menu crash on Qt >= 4.6 has been fixed (resolving bug #2972603).
  • An ancient double-free corruption has been finally fixed at the audio/MIDI bus connection persistence logic.
  • Improved visibility of track state buttons text (R, M, S) when turned on dark colored themes.
  • LV2 Save/Restore extension support kicks off.
  • MIDI engine read-ahead period has been shortened to half than it was since inception--now it's a 500msec cycle.
  • MIDI clip editor event list gets its due inline editing, for time, note, value/velocity and duration columns, just
    one double-click away over the target cell ;)
  • Add-plugin selection dialog position and extent are now remembered across invocations and application sessions
    (tipping by Frank Neumann).
  • MIDI clip time-stretching is now made available through the same gestures as audio ones, by just shift+dragging
    either of the clip edges.
  • Drag-and-copying plug-in instances (cloning) is now fixed with regard to parameter value replication.
  • MIDI clip editor snap-per-beat setting is now independent from main multi-track view; File/Save As... dialog fixed;
    the current event selection is now kept floating as long as it's possible after editing command actions; finally,
    edit mode has been extended to free-hand event drawing, chalking off (piano roll) draw mode from the TODO list.
  • Swing-quantize has finally made its overdue debut as an additional MIDI clip editor tool (see Tools/Quantize...).
  • Almost since its inception, audio inserts were injecting garbage random noise when not being activated, now fixed.
  • Dedicated audio output ports for MIDI track plugins, now have their connection persistence back in business due on session load.

Cheers && Enjoy (what else?)


I tried it under Ubuntu 9.10 (from sources). Preferences dialog doesn't unblock OK button when something changed, though, it asks wether to apply changes or not.

rncbc's picture

Preferences dialog or is it File/Properties... dialog? This looks for essential session property that you must fill in no matter what: its name.


here fresh Ubuntu 10.04 install.... tried new qtracor version but buggy.... doesn't launch : segmentation error....

rncbc's picture

Can you try using gdb or strace and let it be known where or what precisely is crashing? Usual suspects are missing or bad libslv2 dependencies like librdf, librasqal or whatever ...

Please give more details about your system and installation.


I have a Ubuntu 10.04 newly installed.
Jack2. HDA Intel (or UA-25 usb)

libslv2 is installed and the other ones you mentionned as well...
In fact it is just that when I click on qtractor's icon, the interface appears during less than half a second and then vanishes...
All is working well if I reinstall the previous version of Qtractor.


rncbc's picture

I guess you've installed from one of the debs above...

Any chance in summoning the beast from source?


Sorry. I mean View/Options (by F12 key).

rncbc's picture

Ok. Please. check for invalid option values. Most specially some filenames (like New session template) that must exist, otherwise the OK button will stay grayed until you disable the offending option or set it a valid value (existing file).


Aaargh, sorry! I found a blocker. I switched FLAC 32-float sample format for export/capture functions. 8) So, may be, bug is that settings are saved when I say "Yes"? ;)
IMO, better behaviour is to not show sample format items, unavailable for selected file format.

Thanks very much for taking the trouble to provide us with .deb files, Rui. Sadly, I can't comment on your latest offering yet as, similar to a poster above, Qtractor folds on start up on my amd64 machine.

I ran it as root in the terminal and received (from memory only!) this output:-

[2] 2011
[1] Segmentation fault

if that's any help?

I guess this is the boring bit, especially when your 'testers' go into hysterics (me included!) the moment words like 'source' and 'dependencies' are mooted! ;-)

I admire your tenacity...

rncbc's picture

OK. Please install gdb if not already and then try this on a (terminal) command line:

gdb qtractor

and enter at the gdb prompt:

(gdb) run

there, qtractor will start running, hopefully and at some later point it should appear this message saying something like

Program received signal SIGSEGV, Segmentation fault

telling you the program crashed. That's when you ask for a backtrace:

(gdb) bt


(gdb) thread apply all bt

and paste here the spitted cryptic output, letting me inspect that.


Hi Rui, doesn't look very helpful to me (all those question marks) but here goes:-

Reading symbols from /usr/bin/qtractor...(no debugging symbols found)...done.
(gdb) run
Starting program: /usr/bin/qtractor
[Thread debugging using libthread_db enabled]
[New Thread 0x7fffe2d9e710 (LWP 1634)]

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7deb7dd in ?? () from /lib64/

(gdb) thread apply all bt

Thread 2 (Thread 0x7fffe2d9e710 (LWP 1634)):
#0 0x00007ffff4b1f85c in pthread_cond_wait@@GLIBC_2.3.2 ()
from /lib/
#1 0x00007ffff7bcaa5b in ?? () from /usr/lib/
#2 0x00007ffff4b1a9ca in start_thread () from /lib/
#3 0x00007ffff40ca69d in clone () from /lib/
#4 0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7ffff7fcb780 (LWP 1631)):
#0 0x00007ffff7deb7dd in ?? () from /lib64/
#1 0x00007ffff7df2445 in ?? () from /lib64/
#2 0x000000000043fc93 in ?? ()
#3 0x0000000000460a2a in ?? ()
#4 0x00000000004e759d in ?? ()
#5 0x0000000000548ea4 in ?? ()
#6 0x000000000054d638 in ?? ()
#7 0x0000000000552a42 in ?? ()
#8 0x0000000000553357 in ?? ()
#9 0x00000000004307df in ?? ()
#10 0x00007ffff4002c4d in __libc_start_main () from /lib/
#11 0x0000000000430369 in ?? ()
#12 0x00007fffffffe3d8 in ?? ()
#13 0x000000000000001c in ?? ()
#14 0x0000000000000001 in ?? ()
#15 0x00007fffffffe670 in ?? ()
#16 0x0000000000000000 in ?? ()

Boa sorte? ;-)

rncbc's picture

Damn *#?!, I should know better that without debug info included the gdb backtraces are pretty useless :( sorry for the trouble, but no, all those question marks doesn't make it any helpful.

I guess my debs are really broken so forget them, it's no use.

But now that falkTX (viva!:) is with us, who already had success (see above), maybe he can bring us a sane deb packaging. I'm sure he's got some PPA around :) or at least one can borrow from his KXStudio distro ?

Cheers && Viva!

Without excellent PPA'ers like falkTX some of us old noodlers would still be chained to windoze ;(

Note that AutoStatic's got 0.4.6 going okay - and he knows what he's doing in Linux - so you can almost certainly put the problem down to user error or more likely 'user ignorance' ;-)

Hello Rui,

Thanks for this new version! Works well for me, I haven't run in any errors or segfaults yet. So thanks again for maintaining this marvellous piece of software.



Olá Rui!

here's the output from "r" on gdb:
warning: the debug information found in "/lib/" does not match "/lib/" (CRC mismatch).
warning: the debug information found in "/usr/lib/debug//lib/" does not match "/lib/" (CRC mismatch).
warning: the debug information found in "/usr/lib/debug/lib/" does not match "/lib/" (CRC mismatch).
[Thread debugging using libthread_db enabled]
[New Thread 0xf4e87b70 (LWP 15307)]
[New Thread 0xf4e06b70 (LWP 15308)]
Program received signal SIGSEGV, Segmentation fault.
0xf7fee157 in ?? () from /lib/

#0 0xf7fee157 in ?? () from /lib/
#1 0xf7ff3e80 in ?? () from /lib/
#2 0x0807d04c in ?? ()
#3 0x0809ddc8 in ?? ()
#4 0x081253fa in ?? ()
#5 0x0818afcd in ?? ()
#6 0x0818fa87 in ?? ()
#7 0x08194c1b in ?? ()
#8 0x081955b3 in ?? ()
#9 0x0806e0dc in ?? ()
#10 0xf6b55bd6 in __libc_start_main (main=0x806dca0, argc=1, ubp_av=0xffffd4f4, init=0x8222b60, fini=0x8222b50, rtld_fini=0xf7feeb50, stack_end=0xffffd4ec)
at libc-start.c:226
#11 0x0806dc01 in ?? ()

I hope this helps.
(It seems that your ubuntu 10.04 packages are broken, installing from source fixes the issue)

i'm "falktx" at #lad IRC

rncbc's picture

@falkTX viva!

it seems they are indeed. I confess I am not keen to debian/ubuntu packaging at all ;) The system where I get to build those debs is this xubuntu 9.10 guest on a VirtualBox which got ultimately (dist)upgraded to 10.04. Can't really tell what's actually broken as it all runs fine on these boxes (both i386 and amd64).

Maybe I should scrap this ubuntu packaging once and for all and let you ubuntunese gurus do your stuff :) -- burro velho não aprende línguas novas ;)

Seeya (i'm "rncbc" at #lad, #jack and #qtractor, when online of course:))

Hi Rui again!

I indeed have ubuntu packages on my PPA:
(on the bottom)

They don't provide VST and Jack Session support though.
(Cannot compile VST stuff on a PPA...; and my PPA has Jack2, which doesn't have jack-session yet)

I also tested these packages in Jack1, so it's safe to use on any Ubuntu 10.04

rncbc's picture

Awesome, many thanks @falkTX

No big deal re. missing VST and JACK session support; those things are both more oriented for ppl who have no scruples in building it all from source ;)

Ah, now that there's a sane ubuntu packages in town, I may start ditching mine broken ones, or... can I hear a faint plea otherwise?


I really want VST support in QTractor, so I'll compile +VST-support debs next week (need to reformat my PC)
those won't build on launchpad, but rather my pc, using VirtualBox for 32bit (I only use 64bit).

I'll let you know how it goes.

PS: I hope to find you on IRC!

FYI, packages for Karmic are available now too:



rncbc's picture


Error it's always a mixed feeling.

We (may I?) *nix old-farts usually dismiss most problems as PEBCAK but, quite really, problem is in the "we" part of the process. Yeah. most of the times "we" assume that B is doing it, than C will be fine. Eventually, when D gets to it plain wrong, "we" always forget that it is A who ran the whole damn thing havoc. :]



Just backing up a moment, Rui, where you said in your release notes:- "Almost since its inception, audio inserts were injecting garbage random noise when not being activated, now fixed."

There's a classic example in itself! To you, that's a bug - to me. it was a feature, being the only way for a while I could tell whether a plugin was even communicating or not ;-) I even used it creatively on one track ;-)

Perhaps the mos'excellently cool and helpful AutoStatic/Jeremy could let you know just how he's got 0.4.6-4 running without problems - there, maybe, lies the key to why us lesser mortals have hit a brick wall?

QED. Your .debs _do_ work for someone or did he compile from source? {;-)

Hello danny_g, I use my own packages from my own PPA. So those packages are compiled from source. I don't use Rui's packages since those are for Lucid and I don't use Lucid (yet).



As promised, here are the ubuntu 10.04 packages, with everything enabled, except for the (experimental) jack-session:

@Rui: Please update/replace the ones on Qtractor website, as they are totally useless at the moment...

Thanks for your great work!

rncbc's picture

@falkTX: thanks. links are being promptly updated:


Co-operation in action. Love it! ;-)

Thanks so much to both of you. Roll on Qtractor in UbuntuStudio's Synaptic Main!

has anybody ever compiled this successfully on a mac? i get the "Qt library version >= 4.1... no; Qt 4.1 or greater is required" error no matter what i do. i have qt 4.6 installed. tried macports (also the devel version) and the dmg. tried to all kinds of --with-qt folders. is there a definitive guide on installing on a mac? i'd like to compile from source though, in case a package is planned.

rncbc's picture

May I assume you're asking for a MacOSX build ? If yes, then you better know right now that's NOT going to happen, no matter which Qt version you're into.

Qtractor is currently a Linux only application due to its hard-dependency on ALSA for MIDI infrastructure.

Sad but true :)

Thanks anyway, for asking

qtractor is quite impressive. It's a pity I cannot use it with files bigger than about 350 kB in size, in one single track - this is from straight midi recording, in time scales beyond an hour.

I waited, if this weakness would be taken care of, at some time during versions progress - but maybe I am the only one encountering this situation. In fact, this problem appears as a bug: In that case, import of the midi-file takes much longer, and after that, the file is kind of folded or wrapped, so different parts of the file (some two or three) appear like being merged upon each other. so the track is garbled. So, on first sight it looks like kind of memory overflow.

Interesting enough, having compiled qtractor freshly, this problem is not there immediately, but it appears after its third or so use and remains after that. I tried chasing the directly associated configuration and history footprint, but could not see on that level, where the problem is introduced.

This situation is stable behavior since quite some kernel versions now, and slackware-current has distributed quite some upgraded library versions meanwhile.

qtractor would be quite a bit more modest in use of resources than rosegarden, which works as expected.


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